Automatic temperature recording may allow early detection of disease, estrus, heat stress, and the onset of calving. The phase IV Cattle Temperature Monitoring System (MaGiiX Inc., Post Falls, ID) utilizes a passive bolus equipped with a temperature sensor, a stationary panel reader to query the bolus, and software to collect, analyze, and display data. One potential limitation to collection of reticular temperatures is the effect of water temperature and consumption on recorded temperatures. Two replicated 3 x 3 Latin square experiments were conducted at the Purdue Dairy Research and Education Center to assess the impact of water intake on reticular temperatures using the Cattle Temperature Monitoring System. Nine high-producing, mid-lactation, second-parity cows with low somatic cell counts were selected. Before administering a water treatment, access to feed and water was restricted for at least 2 h. Baseline reticular temperatures were established from measurements before water intake. In experiment 1, treatments were 25.2 kg of hot water (34.3 degrees C +/- 1.0), warm water (18.2 degrees C +/- 0.4), or cold water (7.6 degrees C +/- 0.4). In experiment 2, treatments were 18.9 kg of body-temperature water (38.9 degrees C +/- 0.2), cold water (5.1 degrees C +/- 0.4), or control (no water). Following water intake, reticular temperatures were collected for 3 h. In experiment 1, an initial dramatic decrease in reticular temperature was observed followed by a gradual increase toward baseline. Least squares means for maximum drop in temperature were 8.5 +/- 0.5, 6.9 +/- 0.5, and 2.2 +/- 0.5 degrees C for cold, warm, and hot water treatments, respectively. Yet at 3 h, reticular temperatures did not return to the baseline. In experiment 2, control cows remained within the baseline confidence interval through the observation period, and cows receiving body temperature water experienced an initial decrease in temperature (0.4 +/- 0.2 degrees C) with a return to within the baseline confidence interval within 15 min. Cows receiving cold water did not return to within the baseline confidence interval after a large decrease of 9.2 +/- 0.2 degrees C during the 3-h observational period. Moreover, a regression analysis of continued ascent in temperatures predicted that temperatures would return to baseline within 3.5 h. These results demonstrate that, when cows consume large quantities of cold water, the effect of water intake is sizable and sustained. The value of reticular temperatures for daily monitoring in a production setting hinges largely on the implications of this impact.

The Phase IV Cattle Temperature Monitoring System (CTMS; Phase IV Engineering Inc., Boulder, CO) marketed by MaGiiX (MaGiiX Inc., Post Falls, ID) uses a passive bolus equipped with a temperature sensor, a panel reader placed at a parlor entrance or exit to query the bolus, and a software package to collect, analyze, and view data. The biologically inert bolus resides in the cow's reticulum and is queried each time the cow passes the reader. Reticular temperature (RETT) and rectal temperature (RECT) were recorded simultaneously in the milking parlor exit lane in 4 consecutive milkings in each of 4 seasons, totaling 16 measurements per cow. The RETT were obtained by using the phase IV CTMS, whereas the RECT were obtained manually with a GLA M750 thermometer (GLA Agricultural Electronics, San Luis Obispo, CA). Data were edited to remove RETT likely to have been affected by a recent drinking bout. For the 2,042 observations used in analyses, means (+/-SD) were 39.28 (+/-0.41), 38.83 (+/-0.36), and 0.45 (+/-0.33) for RETT, RECT, and the difference between RETT and RECT, respectively. The RETT and RECT were strongly correlated (r = 0.645). The relationship between RETT and RECT varied by season, milking, housing system, and parity. Because dairy producers and veterinarians are accustomed to viewing rectal temperatures, equations to adjust reticular temperatures to a rectal-based scale may increase the utility of the phase IV CTMS. The resulting conversion equations were RECT = 19.23 + 0.496(RETT) for the a.m. milking and RECT = 15.88 + 0.587(RETT) for the p.m. milking.

Maintaining metabolic balance is a key factor in the health of dairy cattle during the transition from pregnancy to lactation. Little is known regarding the role of the circadian timing system in the regulation of physiological changes during the transition period. We hypothesized that disruption of the cow's circadian timing system by exposure to chronic light-dark phase shifts during the prepartum period would negatively affect the regulation of homeostasis and cause metabolic disturbances, leading to reduced milk production in the subsequent lactation. The objective was to determine the effect of exposure to chronic light-dark phase shift during the last 5 wk prepartum of the nonlactating dry period on core body temperature, melatonin, blood glucose, β-hydroxybutyric acid (BHB) and nonesterified fatty acid (NEFA) concentrations, and milk production. Multiparous cows were moved to tiestalls at 5 wk before expected calving and assigned to control (CTR; n = 16) or phase-shifted (PS; n = 16) treatments. Control cows were exposed to 16 h of light and 8 h of dark. Phase-shifted cows were exposed to the same photoperiod; however, the light-dark cycle was shifted 6 h every 3 d until parturition. Resting behavior and feed intake were recorded daily. Core body temperature was recorded vaginally for 48 h at 23 and 9 d before expected calving using calibrated data loggers. Blood concentrations of melatonin, glucose, BHB, and NEFA were measured during the pre-and postpartum periods. Milk yield and composition were measured through 60 DIM. Treatment did not affect feed intake or body condition. Cosine fit analysis of 24-h core body temperature and circulating melatonin indicated attenuation of circadian rhythms in the PS treatment compared with the CTR treatment. Phase-shifted cows had lower rest consolidation, as indicated by more total resting time, but shorter resting period durations. Phase-shifted cows had lower blood glucose concentration compared with CTR cows (4 mg/mL decrease), but BHB and NEFA concentrations were similar between PS and CTR cows. Milk yield and milk fat yield were greater in PS compared with CTR cows (2.8 kg/d increase). Thus, exposure to chronic light-dark phase shifts during the prepartum period attenuated circadian rhythms of core body temperature, melatonin, and rest-activity behavior and was associated with increased milk fat and milk yield in the postpartum period despite decreased blood glucose pre-and postpartum. Therefore, less variation in central circadian rhythms may create a more constant milieu that supports the onset of lactogenesis.